Moisture stable polyurethane biasable transfer members

ABSTRACT

The invention provides rolls, belts and other biasable members having at least one layer or coating of an elastomeric resilient polyurethane formed by reacting (a) a polyisocyanate prepolymer comprising the reaction product of a saturated aliphatic polyisocyanate, a saturated cycloaliphatic polyisocyanate, or an aromatic polyisocyanate and a polyol free of aliphatic unsaturation, preferably a polyalkylene glycol in which the alkylene group contains 2 to 8 carbon atoms, and (b) a hardening mixture comprising a polyol of (a) or a diamine free of aliphatic unsaturation, or a mixture thereof and, as a conductivity control agent, from 0.001 to 5.0 weight percent, based on the total weight of (b), of a complex of ethylene glycil or an oligoethylene glycol selected from the group consisting of di-, tri- and tetraethylene glycol with an ionizable ferric halide salt selected from the group consisting of ferric flouride, ferric chloride and ferric bromide.

FIELD OF THE INVENTION

This invention relates generally to the field of electrostatography.More particularly, the invention relates to electrically biasabletransfer members for use in electrostatographic transfer processes fortransferring toner images from one support surface to another and tomethods for their preparation.

BACKGROUND

In electrostatography, an image comprising an electrostatic fieldpattern, usually of non-uniform strength, (also referred to as anelectrostatic latent image) is formed on an insulative surface of anelectrostatographic element by any of various methods. For example, theelectrostatic latent image may be formed electrophotographically (i.e.,by imagewise photo-induced dissipation of the strength of portions of anelectrostatic field of uniform strength previously formed on a surfaceof an electrophotographic element comprising a photoconductive layer andan electrically conductive substrate), or it may be formed by dielectricrecording (i.e., by direct electrical formation of an electrostaticfield pattern on a surface of a dielectric material). Typically, theelectrostatic latent image is then developed into a toner image bycontacting the latent image with charged toner particles. If desired,the toner image can then be transferred to a final support material orreceiver such as a web or sheet of paper and affixed thereto to form apermanent record of the original.

Historically, the transfer of toner images between supporting surfaceshas been accomplished with the electrostatic transfer of either acorotron or a roller or belt electrode biased to a certain potential,such electrode being referred to as a bias transfer member (roll orbelt). In corona-induced transfer as, for example, disclosed byVandenberg in U.S. Pat. No. 2,836,725, the final support sheet is placedin direct contact with the toner image while the image is supported onthe photoconductive surface. The back of the sheet, that is, the sideaway from the image, is sprayed with a corona discharge having apolarity opposite to that carried by the toner particle causing thetoner to be electrostatically transferred to the sheet. The corotronsystem is relatively simple. The charges deposited electrostaticallytack the final support material, such as paper, to the original tonersupport, such as, the photoconductor, in addition to creating thedesired electric field affecting transfer of the toner to the paper.However, the strong attraction between the paper and the original tonersupport makes it mechanically difficult to separate the two supports.

Transfer of developed images from the photoconductor to the finalsupport material with the aid of a biased transfer member, such as abiased transfer roll, as a means of controlling the forces acting on thetoner during transfer and of avoiding the severe tacking problemsencountered with the use of the corona induction system have been triedwith limited success. A bias transfer member is a member forelectrically cooperating with a conductive support surface to attractelectrically charged particles from the support surface towards themember. Bias transfer members are well known in the art. A bias transferroll is disclosed by Fitch in U.S. Pat. No. 2,807,233, where a metalroll coated with a resilient coating having a resistivity of at least10⁶ ohm cm is used as a bias transfer member. Because of the resistivityof the coating, the amount of bias that can be applied to the roll islimited to relatively low operating values because, at the higherranges, the air in or about the transfer zone begins to break down,i.e., ionizes causing the image to be degraded during transfer. Shelffo,in U.S. Pat. No. 3,520,604, discloses a transfer roll made of aconductive rubber having a resistivity in the range of 10¹⁶ to 10¹¹ ohmcm. Here, in order to give the roll the needed resiliency required inmost practical applications, the coating must be relatively thick. Athick coating of high resistivity acts to build up a surface charge onthe roll resulting in air break down in the transfer region andeventually copy degradation.

More recently, improved bias transfer members have been disclosed whichreportedly have overcome many of the electrical and image degradationproblems associated with some of the previous transfer techniques.Dolcimascolo et al, in U.S. Pat. No. 3,702,482, disclose a multiplelayer transfer roll member for transferring xerographic images undercontrolled conditions. The member is capable of electrically cooperatingwith a conductive support surface to attract charged toner particlesfrom the support surface towards the member or towards a transfermaterial such as paper positioned therebetween, the member having aconductive substrate for supporting a biased potential thereon, anintermediate blanket (primary layer) placed in contact with thesubstrate to the outer periphery of the blanket and a relatively thinouter coating (secondary layer) placed over the blanket layer having anelectrical resistivity to minimize ionization of the atmosphere when thetransfer member is placed in electrical cooperation with the imagesupport surface and providing a good toner release property enabling thedevice to be cleaned of the toner. Meagher, in U.S. Pat. No. 3,781,105,discloses a similar transfer member employed in conjunction with avariable electrical bias means for regulating automatically theelectrical field levels at various points on the transfer member duringthe transfer operation and providing constant current control.

In the preferred embodiment, the transfer members disclosed in U.S. Pat.No. 3,702,482 and U.S. Pat. No. 3,781,105, consist of a roller having acentral biasable conductive core further having an intermediate blanketor electrically "relaxable" layer (primary layer) surrounding and inelectrical contact with the core, and further having a second blanket orelectrically "self-leveling" outer layer (secondary layer) surroundingand in electrical contact with the primary layer. Under operatingconditions, it is desirable for optimal image transfer to maintain arelatively constant current flow of less than about 30 micro amps in thenip area between the transfer roll surface, transfer material, andphotoconductive surface from which a developed image is to betransferred. For this condition to exist at given potentials, theresistivity of the primary and secondary layers must be within criticalvalues and preferably be relatively constant under normally anticipatedextremes of operating conditions. Preferably, it has been found that theprimary layer should be a resilient elastomeric material having a volumeresistivity within the range of 10⁷ to less than 10¹¹ ohm cm, and thesecondary layer should also be a resilient material having a volumeresistivity within the range of 10¹¹ to 10¹⁵ ohm cm.

In practice, it has been found that the elastomeric polyurethanematerials which are used in the transfer member, and which exhibitresistivities within the above ranges, or the resistivities of which canbe adjusted or controlled to within the above ranges, are moisturesensitive such that the resistivity may vary by as much a factor of 50between 10% and 80% relative humidity as a function of the amount ofmoisture absorbed from or lost to the surrounding atmosphere. Forexample, in the case of the polyurethane materials which are employed asthe primary layer and which have exceptionally good electricalcharacteristics, the volume resistivity may change from 10¹¹ ohm cm atlow moisture contents, i.e., less than about 0.1% moisture, to 10⁹ ohmcm at higher moisture levels, i.e., about 2.5% moisture. Otherpolyurethanes suitable for use as the secondary layer exhibitresistivity variations from about 10¹⁵ to 10¹³ ohm cm as a function ofincreasing moisture content. The consequent variations in resistivitydue to relative humidity effects will ordinarily give rise to erraticperformance of the transfer member from day to day particularly in termsof transfer efficiency, i.e., the quality of the image transferredunless compensated for by a concomitant change in the voltagessufficient to maintain a constant nip current, as disclosed by Meagher,in U.S. Pat. No. 3,781,105.

Several attempts have been made in the past to control both theresistivity of such materials to within the critical ranges necessaryfor optimal image transfer and, at the same time, to reduce the moisturesensitivity of such materials to changes in relative humidity so thatthe resistivity of the materials remains relatively constant within theranges required for optimal image transfer. For example, Seanor et al,in U.S. Pat. No. 3,959,574, disclose that the resistivity of theelastomeric materials which constitute the primary layers of themultiple layer transfer roll members of Dolcimascolo et al, can becontrolled to within the preferred resistivity range of about 10⁷ toabout 10¹¹ ohm cm and can be rendered less sensitive to changes inrelative humidity by the addition of certain ionic compounds or agentsto the elastomeric materials. Particularly preferred additives disclosedby Seanor et al are quaternary ammonium compounds, includingtetraheptylammonium bromide, trimethyloctadecylammonium chloride, andbenzyltrimethylammonium chloride. The additive compounds or agents ofSeanor et al are worked into the polyurethane by direct melting of theadditive into the polyurethane or by incorporating a solution ordispersion of the additive into the polyurethane. As a result of thesemethods of incorporation, the additive agents of Seanor et al are notanchored in the elastomeric composition and are leached out of theelastomer over time during normal operating conditions which results ina decline in the level of conductivity in the polyurethane elastomers.

Chen et al, in U.S. Pat. No. 4,729,925, and U.S. Pat. No. 4,742,941disclose, as coating materials for biasable transfer members,polyurethane elastomers made from certain polyisocyanate prepolymers andpolyols in which the resistivity can be maintained between 1.0×10⁹ and1.0×10¹¹ ohm cm by copolymerizing with the polyisocyanate prepolymersand polyol hardening compounds used to make the polyurethane elastomerscertain polyol charge-control agents formed from certain metal saltscomplexed with particular polyether diols such as, for example,bis[oxydiethylenebis(polycaprolactone)yl]5-sulfo-1,3-benzenedicarboxylate,methyltriphenylphosphonium salt. Unlike the additive control agents ofSeanor et al, the polyol charge-control agents of Chen et al are notprone to being leached out of the elastomer during normal usage sincethey constitute an integral part of the cured polyurethane elastomerinto which they are incorporated by virtue of having been copolymerizedwith the polyisocyanate prepolymers and polyol components used to makethe polyurethane during the preparation of the elastomer. Thepolyurethane elastomers of Chen et al, however, are moisture sensitive.Reference to curve 2 in FIG. 2 of U.S. Pat. No. 4,729,925, indicates,for example, that the volume resistivity of the conductive polyurethaneelastomer of Example 15 prepared from a commercial polyurethane mix andthe polyol control agent of Example 10 therein, i.e.,bis[oxydiethylenebis-(polycaprolactone)yl]-5-sulfo-1,3-benzenedicarboxylate,methyltriphenylphosphonium salt, decreased by a factor of about 6.5 whenthe relative humidity changed from to about 85%.

In U.S. Pat. No. 5,011,739, issued Apr. 30, 1991, entitled "MoistureStable Biasable Members and Method for Making Same", to Nielsen et al,there is disclosed, as coating materials for biasable transfer members,certain crosslinked polyurethane elastomers which are not subject tothese problems. The coating compositions disclosed in theabove-mentioned U.S. Pat. No. 5,011,739, are formed by reacting:

(a) a polyisocyanate prepolymer comprising the reaction product of:

(i) polyisocyanate, and

(ii) a polyether polyol selected from the group consisting of apolyalkylene glycol having 2 to 3 carbon atoms in the alkylene group;and

(b) a hardening mixture comprising:

(i) a polyether polyol selected from the group consisting of apolyalkylene glycol having 2 to 3 carbon atoms in the alkylene groupand,

(ii) as a conductivity-control agent for controlling the resistivity ofthe elastomeric polyurethane, from 0.01 to 3.0 weight percent based onthe total weight of

(b) of a complex of an oligoethylene glycol selected from the groupconsisting of di-, tri- and tetraethylene glycol with an ionizablealkali metal salt selected from the group consisting of sodium iodide,lithium iodide and sodium thiocyanate.

The conductivity control agent containing crosslinked polyurethaneelastomers described, when used as coating materials for biasabletransfer members, provide biasable transfer members capable ofelectrically cooperating with a conductive support surface to attractcharged toner particles towards the member or towards a transfermaterial such as a sheet of paper positioned between the member and theconductive support in which the volume resistivity not only can becontrolled or adjusted to within a specific range necessary for optimalimage transfer, (i.e., from about 10⁷ to about 5.0×10¹⁰ ohm cm), butalso one in which the resistivity is substantially insensitive to widelyvarying changes in relative humidity encountered during normal operatingconditions such that the resistivity remains relatively constant withinthe range required for optimal image transfer. Further, since theconductivity control agents utilized by Nielsen et al are covalentlybonded to the backbone and/or the crosslinking portion of thepolyurethane elastomer during formation or preparation of the elastomer,there also is provided a coating material for use in a biasable transfermember in which the conductivity control agents used therein are notprone or subject to being leached out of the elastomer over time duringnormal operating conditions thereby causing a decline in the level ofconductivity in the polyurethane elastomer.

While the biasable transfer members disclosed and described inaforementioned U.S. Pat. No. 5,011,739 constitute a significantadvancement in the art by providing biasable transfer members in whichthe resistivity not only can be controlled or adjusted to within aspecific range necessary for optimal image transfer, but also one inwhich the resistivity is substantially insensitive to widely varyingchanges in relative humidity encountered during normal operatingconditions such that the resistivity remains relatively constant withinthe range required for optimal image transfer, it is desired that evenfurther improvements in this regard be made, particularly with respectto further reducing the sensitivity of the volume resistivity ofbiasable transfer members to changes in relative humidity. The presentinvention provides such a biasable transfer member and a method ofmaking same.

SUMMARY OF THE INVENTION

The present invention provides a biasable transfer member, that is, amember capable of electrically cooperating with a conductive supportsurface to attract charged toner particles from the support surfacetowards the member. The biasable transfer member comprises a conductivesubstrate capable of supporting a uniform bias potential thereon and atleast one coating comprising a resilient elastomeric polyurethane formedby reacting:

(a) a polyisocyanate prepolymer comprising the reaction product of:

(i) a saturated aliphatic polyisocyanate, a saturated cycloaliphaticpolyisocyanate or an aromatic polyisocyanate; and

(ii) a polyol free of aliphatic unsaturation; and

(b) a hardening mixture comprising:

(i) a polyol of (a) (ii) or a diamine free of aliphatic unsaturation, ora mixture thereof; and,

(ii) as a conductivity-control agent for controlling the resistivity ofthe elastomeric polyurethane, from 0.001 to 5.0 weight percent, based onthe total weight of (b), of a complex of ethylene glycol or anoligoethylene glycol selected from the group consisting of di-, tri- andtetraethylene glycol with an ionizable ferric halide salt selected fromthe group consisting of ferric fluoride, ferric chloride and ferricbromide,

the coating being in electrical contact with the conductive substrateand having an electrical resistivity such that the coating is capable oftransmitting a bias potential from the substrate to the outer peripheryof the coating.

Since the conductivity agent disclosed and described herein functions tocontrol or alter the resistivity of the elastomeric polyurethane intowhich it is incorporated, the invention also provides, in anotherembodiment, a method of controlling the resistivity of a member forelectrically cooperating with a conductive support surface, such as aphotoconductive surface, to attract charged toner particles from thesurface towards the member, which method comprises coating a conductivesubstrate capable of supporting a uniform bias potential thereon with atleast one coating of a resilient elastomeric polyurethane, said coatingbeing in electrical contact with the conductive substrate and formed byreacting:

(a) a polyisocyanate prepolymer comprising the reaction product of:

(i) a saturated aliphatic polyisocyanate, a saturated cycloaliphaticpolyisocyanate or an aromatic polyisocyanate; and

(ii) a polyol free of aliphatic unsaturation: and

(b) a hardening mixture comprising:

(i) a polyol of (a) (ii) or a diamine free of aliphatic unsaturation, ora mixture thereof; and,

(ii) as a conductivity control agent to alter the resistivity of theelastomeric polyurethane, from 0.001 to 5.0 weight percent, based on thetotal weight of (b), of a complex of ethylene glycol or an oligoethyleneglycol selected from the group consisting of di-, tri- and tetraethyleneglycol with an ionizable ferric halide salt selected from the groupconsisting of ferric fluoride, ferric chloride and ferric bromide,

whereby the elastomeric polyurethane having an altered resistivity iscapable of transmitting a bias potential from the substrate to the outerperiphery thereof.

By the use of the term "bias transfer member" or "bias transfer roll",is meant a member or roll for electrically cooperating with a conductivesupport surface to attract electrically charged particles from thesupport surface towards the member. In particular, a bias transfer rollis one which electrically cooperates with a photoconductive surface orsupport, such as a photoconductive plate or photoconductor, when broughtinto contact therewith, to attract charged toner particles from theplate in the direction of the roll. In this manner, the developed imagesare transferred from the photoconductor to a final support material,such as paper or the like.

Important advantages of the polyurethane coatings of the biasabletransfer members of the invention are that they possess the capabilityto retain pre-established levels of resistivity and exhibit enhancedmoisture insensitivity.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view in partial section showing the constructionof a biasable transfer roll of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The biasable transfer members of the present invention have applicationin any suitable electrostatographic device such as, for example, anelectrophotographic device, in which a transfer member, moreparticularly, a bias transfer roll, is used for electrically cooperatingwith a photoconductive element, plate or surface when brought intocontact therewith to attract toner particles bearing an electrostaticcharge on the element or plate toward the roll. Transfer isaccomplished, as in the prior art, by feeding a sheet of transfermaterial into the nip region formed by the surface of the transfer rolland the surface of a photoconductive insulating material or elementbearing a developed image and imposing a potential on the transfer rollsufficient to cause the transfer of the toner particles or material fromthe surface of the photoconductive insulating material or element to theadjacent surface of the transfer material. In practice, any source ofelectrical power connected to the central conductive core of thetransfer roll and capable of placing the transfer roll member at apotential sufficient to attract toner images from the photoconductiveinsulating surface toward the roll may be employed. A more completediscussion of the principles and configurations involved in bias rolltransfer may be found in U.S. Pat. Nos. 2,951,443; 3,620,616; 3,633,543;3,781,105; or 3,708,482.

Referring specifically to FIG. 1, there is shown a cut-away view of atransfer member illustrating the internal construction thereof. Thetransfer member is in the form of a roll and is basically formed upon arigid hollow cylinder 1 that is fabricated of a conductive metal, suchas aluminum, copper or the like, capable of readily responding to abiasing potential placed thereon. Over core 1 is placed a coating 2which is a crosslinked or non-crosslinked elastomeric polyurethanecontaining a conductivity control agent capable of altering orcontrolling the resistivity of the polyurethane to within a preferredresistivity range consistent with optimal image transfer and which isbonded covalently to the elastomeric network or matrix of thepolyurethane, i.e., to the backbone, crosslinking or branched portion ofthe polyurethane elastomer.

Outer coating 2 which is formed of the resilient elastomeric materialcan be designed to have a hardness of between about 10 Shore A to about80 Shore D, and preferably about 15-100 Shore A and may be about 0.125inch (0.318 cm) to about 0.625 inch (1.58 cm) in thickness, preferablyabout 0.30 inch (0.762 cm) in thickness, having sufficient resiliency toallow the roll to deform when brought into moving contact with aphotoconductive drum surface to provide an extended contact region inwhich the toner particles can be transferred between the contactingbodies. The elastomeric polyurethane coating should be capable ofresponding rapidly to the biasing potential to impart electrically thecharge potential on the core to the outer extremities of the rollsurface. It is preferred that the polyurethane coating have aresistivity of from about 1.0×10⁷ to about 5.0×10¹⁰ ohm cm, and, morepreferably, from about 2.0×10⁸ to about 2.0×10¹⁰ ohm cm, as this hasbeen found to be most consistent with optimal image transfer. This isachieved by including in the crosslinked or noncrosslinked polymericnetwork of the polyurethane elastomer, the conductivity control agent ofthe present invention. Because the conductivity control agent is bondedcovalently to the elastomeric matrix or network of the polymer, it formsa permanently fixed or integral part of the polymer and will not migratetherefrom in contrast to those prior art conductivity control additiveswhich are worked into the polyurethane by direct melting of the additiveinto the polyurethane or by incorporating a solution or dispersion ofthe additive into the polyurethane. As a result, a permanent, or at thevery least, a relatively constant degree of resistivity is imparted tothe polyurethane elastomer that will not change substantially over timeduring the course of normal operations. In accordance with the presentinvention, the coating of the conductive substrate must be formulated ofat least one layer of an elastomeric polyurethane having covalentlybonded to the crosslinked or non-crosslinked polymeric network thereof,a conductivity control agent capable of altering and/or controlling theresistivity of the elastomer to within the preferred or desiredresistivity range. By coating the biasable transfer member with theseparticular polyurethane elastomers, the resistivity of the biasabletransfer member is controlled and, in addition, the sensitivity of theresistivity of the biasable transfer member also is controlled inrelationship to changes in relative humidity. Thus, the resistivity ofthe elastomeric polyurethanes having conductivity control agents tocontrol the resistivity of the polyurethanes used as the outer coatingof the bias transfer member of FIG. 1 is less sensitive to changes inrelative humidity than elastomeric polyurethanes which are not treatedwith such agents. Examples of the elastomeric crosslinked ornon-crosslinked polyurethane materials having conductivity controlagents included in the crosslinked or non-crosslinked polymeric networksthereof as an integral part of the polyurethane material in the mannerdescribed in accordance with the invention to control the resistivity ofthe elastomer and hence the biasable transfer member are set forthbelow.

The polyurethane elastomers which can be used in accordance with thepresent invention are known polyurethane elastomers which are made fromknown starting materials using methods which are well known in the artfor making polyurethane elastomers plus the conductivity control agentsdescribed herein. The conductivity control agents contain an ionic metalsalt to impart conductivity to the elastomers.

The polyurethane elastomers are the chemical reaction products of (a)polyisocyanate prepolymers formed from an isocyanate (specifically asaturated aliphatic polyisocyanate, a saturated cycloaliphaticpolyisocyanate compound, or an aromatic polyisocyanate compound) reactedwith a polyol free of aliphatic unsaturation, and (b), a hardenercomposition comprising a polyol, as previously described, or a diaminefree of aliphatic unsaturation, or a mixture thereof and an amount ofthe conductivity control agent described hereinbefore sufficient tocontrol the resistivity of the polyurethane elastomer to within a rangeof from about 1.0×10⁷ to about 5.0×10¹⁰ ohm cm, and more preferably,from about 2.0×10⁸ to about 2.0×10¹⁰ ohm cm. The polyurethane elastomerscan be crosslinked or non-crosslinked. If a crosslinked polyurethane isdesired, such an elastomer can be readily formed by using an excess ofpolyisocyanate compound in preparing the elastomer or by utilizing apolyisocyanate, a polyol and/or a polyamine having a functionalitygreater than two in preparing the elastomer.

The polyisocyanate prepolymer can comprise recurring units derived fromany suitable polyol with the proviso that the polyol is free ofaliphatic unsaturation, including for example, amine-based polyols,polyether polyols, polyester polyols, mixtures thereof, and aromatic aswell as saturated aliphatic and saturated cycloaliphatic polyisocyanatesprovided they do not adversely affect or in any way interfere with therelative humidity sensitivity or with the resistivity of thepolyurethane in general. Exemplary polyisocyanate compounds which may beused to make the prepolymer are exemplified by those disclosed in U.S.Pat. Nos. 2,969,386 and 4,476,292, such as 4,4'-diphenylmethanediisocyanate; 1,5-naphthalene diisocyanate; 3-isocyanatomethyl3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate);methylenebis(4-isocyanatocyclohexane); hexamethylene diisocyanate;1,3-cyclohexane bis(methylisocyanate); 2,2,4-trimethylhexamethylenediisocyanate, and combinations thereof, as well as related saturatedaliphatic and cycloaliphatic polyisocyanates which may be substitutedwith other organic or inorganic groups that do not adversely affect thecourse of the polymerization reaction or interfere with the relativehumidity sensitivity or with the resistivity of the polyurethane ingeneral. One preferred polyisocyanate ismethylenebis(4-isocyanatocyclohexane). Another preferred polyisocyanateis toluene diisocyanate.

The term "aliphatic", as used herein, includes those carbon chains whichare substantially non-aromatic in nature. They must be saturated,however, they may be unbranched, branched or cyclic in configuration andmay contain various substituents. Exemplary of long chain aliphaticpolyisocyanates are dodedane diisocyanate, tridecane diisocyanate, andthe like.

The term "aromatic" as used herein, includes a diatropic moiety derivedfrom benzene, naphthalene, anthracene, phenanthrene, biphenyl and thelike. They may be unsubstituted or substituted, for example, with halo,nitro, saturated alkyl, saturated alkoxy, saturated alkylthio or arylsubstituents. Included in this definition are also alkylene diarylstructures, for example, diphenylmethane and 1,2-diphenylethane.Exemplary of aromatic diisocyanates are toluene-2,4-diisocyanate,m-phenylene diisocynate, methylene-di-p-phenyl diisocyanate, and thelike.

Polyols useful in preparing the polyisocyanate prepolymer and finishedpolyurethane elastomers are, as previously described, any suitablepolyol free of aliphatic unsaturation which will not interfere with therelative humidity sensitivity or with the resistivity of thepolyurethane composition or otherwise adversely affect the propertiesand/or the performance of the polyurethane elastomer in effectingoptimal image transfer of the biasable member on which the polyurethaneis coated and can include, for example, amine-based polyols, polyetherpolyols, polyester polyols and mixtures thereof. Examples of suchpolyols are disclosed in U.S. Pat. Nos. 2,969,386; 3,455,855; 4,476,292and 4,390,679. One preferred group of polyols are aliphatic polyols andglycols such as glycerol, trimethylolpropane, 1,3-butylene glycol,1,4-butylene glycol, propylene glycol, hydroxylated castor oils,polyethers such as poly(tetramethylene ether glycols) and poly(propyleneether glycols), low molecular weight polyester polyols, such aspolyethylene adipate, and a poly(caprolactone)diol.

A particularly useful polyol which can be used to prepare thepolyisocyanate prepolymer and/or chain extend the prepolymer to thefinal conductive bulk polyurethane is an aliphatic alkylene glycolpolymer having an alkylene unit composed of at least two carbon atoms,preferably 2 to 8 carbon atoms. These aliphatic alkylene glycol polymersare exemplified by poly(oxyethylene glycol), poly(oxypropylene glycol)and poly(tetramethylene ether glycol). Di-, tri-, and tetrafunctionalcompounds are available with the trifunctional ones being exemplified bythe reaction product of glycerol or trimethylolpropane and propyleneoxide. A typical polyether polyol is available from Union Carbide underthe designation PPG-425.

Another preferred group of polyols are amine-based polyols. A widevariety of aromatic and aliphatic diamines may form part of theamine-based polyols. Such polyols includeN,N,N'N'-tetrakis(2-hydroxypropyl)ethylenediamine and a polymer ofethylene diamine, propylene oxide and ethylene oxide. A typical aromaticamine-based polyol is available from Upjohn under the designationISO-NOL 100; a typical aliphatic amine-based polyol is available fromBASF under the designation QUADROL and a typical ethylenediamine/propylene oxide/ethylene oxide polymer is available from BASFunder the designation PLURACOL 355.

In general, suitable polyols useful for preparing the prepolymer and/orchain extending the prepolymer to the final conductive bulk polyurethanewill have molecular weights of from about 60 to 10,000, typically, fromabout 500 to 3000.

Preferred concentration ranges for the respective components of theprepolymer are 5-40% by weight of polyisocyanate and 60-95% by weightpolyol, based on the total weight of the prepolymer, to form a resinprepolymer.

The final conductive bulk polyurethane elastomer is produced bychain-extending and/or crosslinking the prepolymer with a hardenercomposition comprising at least one additional polyol or blends ofpolyols of the type aforedescribed and discussed hereinabove and theconductivity control agents described hereinbefore.

The polyol hardener system comprises at least one polyol of the typeaforedescribed, such as, for example, an amine-based polyol or apolyether polyol previously identified and defined hereinabove or blendsof these polyols.

A preferred polyol is poly(tetramethylene ether glycol) having addedthereto about 0.001 to about 5.0 weight percent of the total polyolhardener system of the ionic polyol conductivity control agent asdescribed hereinbefore.

Alternatively, in lieu of, or in addition to, utilizing a polyol of thetype and kind described hereinabove in the hardener compositions used toform the presently described polyurethane elastomers, an aliphatic orcycloaliphatic diamine free of aliphatic unsaturation or an aromaticdiamine free of aliphatic unsaturation can be used in the hardenercomposition provided they do not interfere with the relative humiditysensitivity or with the resistivity of the polyurethane elastomercomposition or otherwise adversely affect the properties and/or theperformance of the polyurethane elastomer in effecting optimal imagetransfer of the biasable member on which the polyurethane is coatedalong with the conductivity control agent described hereinbefore.Exemplary diamines which can be used in the hardener compositions of thepresent invention include 4,4'-methylenebis(o-chloroaniline),phenylenediamine, bis(4aminocyclohexyl)methane, isophoronyldiamine, andthe reaction products of anhydrides with such amines as described inU.S. Pat. No. 4,390,679. Preferred such diamines are4,4'-methylenebis(o-chloroaniline), diethyltoluenediamine availablecommercially from Ethyl Corporation, 451 Florida Blvd., Baton Rouge, La.under the trade name Ethacure 100 and di(methylthio)2,4-toluenediamine,also available commercially from Ethyl Corporation under the trade-nameEthacure 300.

Such diamines serve to chain extend the prepolymer to the finalconductive bulk polyurethane. Suitable such diamines will typically havemolecular weights ranging from about 60 to about 500, and are employedin the hardener compositions alone having added thereto from about 0.001to about 5.0 weight percent of the total polymer of the conductivitycontrol agent described hereinabove or as a blend in combination withone or more of the aforedescribed polyol components in weight ratios ofpolyamine to polyol ranging from 1:1 to 1:10 having added thereto fromabout 0.001 to about 5.0 weight percent of the total polymer of theconductivity control agent aforedescribed.

The polyurethanes are prepared by admixing the prepolymer with thepolyol hardener. Catalysts and optional additives also can be includedwithin the hardener or the prepolymer with the provision that they donot interfere with the relative humidity sensitivity or with the volumeresistivity of the polyurethane.

In general, if the hardener contains stoichiometric equivalents lessthan that contained in the prepolymer, a crosslinked polyurethaneelastomer will result. On the other hand, if the hardener containsstoichiometric equivalents greater than or equivalent to that containedin the prepolymer, then a non-crosslinked polyurethane elastomer willresult. This only applies, however, if all the components in theprepolymer and the hardener are difunctional. If any component, eitherin the hardener composition or in the prepolymer composition has afunctionality greater than two, then the resultant polyurethaneelastomer will always be crosslinked.

Further, and if desired, instead of preparing the polyurethaneelastomers of the present invention by first forming a polyisocyanateprepolymer and hardening mixture and then reacting the two together, allof the starting materials required to form the polyurethane elastomersof the present invention may simply be added together, reacted and curedin a "one-shot" method of preparation. Or, still further, theconductivity control agent described hereinabove may be added to thepolyisocyanate prepolymer instead of the hardener and the prepolymercontaining the conductivity control agent and the hardener reactedtogether to form the polyurethane elastomers of the present invention.If either of these two methods of preparation are used, amounts ofconductivity control agent in the range of from about 0.001 to about 5.0weight percent, based on the total weight of the resultant polyurethane,generally will be appropriate for adjusting the resistivity of thepolymer elastomer to within the desired limits.

Catalysts known to those skilled in the art which may be included in thehardener composition may comprise, for example, heavy metals utilized inamounts of about 0.001 to 0.5 % metal, by weight, preferably about 0.1%metal, by weight, of hardener, e.g., organotin, organozinc, mercury,cadmium and magnesium compounds. It has been found, however, that if abismuth-containing catalyst, such as, for example, bismuth neodecanoateis used in preparing the polyurethane elastomers described herein, thatthe mole ratio of the ferric halide conductivity control agent to thecatalyst must be at least 3:1, or higher. Tertiary amines also may beutilized. Examples of some typical catalysts which may be included inthe hardener composition include cadmium 2-ethylhexanoate, cerium2-ethylhexanoate, chromium 2-ethylhexanoate, cobalt 2-ethylhexanoate,cobalt neodecanoate, copper acetylacetonate, iron stearate, magnesiumoleate, manganese 2-ethylhexanoate, molybdenum 2-ethylhexanoate, nickelacetylacetonate, nickel 2-ethylhexanoate, zinc 2-ethylhexanoate,zirconium 2-ethylhexanoate, dibutyltin dilaurate, bismuth neodeconate,bismuth 2-ethylhexanoate, and the like.

Optional additives or addenda which may be included in the hardenercomposition may comprise, for example, anti-foaming agents such asglycerine, and ethyl acrylate-2-ethylhexyl acrylate copolymer, dimethylsiloxane copolymers and other silicones such as SAG-47 commerciallyavailable from Union Carbide Company; antioxidants, such as esters ofβ-(3,3-di-tert-butyl-4-hydroxyphenyl)propionic acid with monohydric orpolyhydric alcohols, for example, methanol, octadecanol, 1,6-hexanediol,neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethyleneglycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, anddi(hydroxyethyl)oxalic acid diamide; UV absorbers and light stabilizerssuch as 2-(2'-hydroxyphenyl)benzyltriazoles and sterically hinderedamines such as bis(2,2,6,6-tetramethylpiperidyl)sebacate,bis(1,2,2,6,6-pentamethylpiperidyl)sebacate,n-butyl-3,5-di-tert-butyl-4-hydroxybenzyl malonic acidbis(1,2,2,6,6-pentamethylpiperidyl)ester condensation product of1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinicacid, condensation product ofN,N'-bis(2,2,6,6-tetramethylpiperidyl)hexamethylenediamine, and4-tert-octylamino-2,6-dichloro-1,3,5-s-triazine,tris(2,2,6,6-tetramethylpiperidyl)nitrolotriacetate,tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarbonicacid and 1,1'-(1,2-ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone);plasticizers such as phthalates, adipates, glutarates, epoxidizedvegetable oils, and the like; fungicides, pigments, dyes; reactive dyes;moisture scavengers; and the like.

The prepolymer-hardener mixtures prior to curing, exhibit sufficientlylow viscosities to facilitate mixing, pouring and air bubble diffusion,thereby allowing for the formation of bubble free castings in theconfiguration of a transfer roller or belt.

Two-component polyurethane mixes of the type described above into whichthe conductivity control agents of the invention can be incorporated arecommercially available. Examples of such commercially availablepolyurethane systems include CONATHANE TU-500 and CONATHANE TU-400available from Conap, Inc., Olean, N.Y., and a system sold by WinfieldIndustries, Inc., Buffalo, N.Y., under the trade name Winthane W643.

The degree of conductivity imparted to the polymer will vary dependingprimarily upon the amount of conductivity control agent included in thecombination of starting materials and the inherent properties of thegiven polymer and crosslinking agent, if employed, (i.e., the degree ofconductivity the polymer would have if no conductivity control agentwere included). Any amount of the conductivity control agent sufficientto adjust or alter the resistivity of the elastomeric polyurethanematerial to within the desired limits, i.e., from higher levels ofresistivity to a resistivity in the range of from about 1.0×10⁷ to about5.0×10¹⁰ ohm cm, or within the range itself, may be used in accordancewith the present invention. Resistivities in this range have been foundto be consistent with optimal image transfer efficiency. In general, asmentioned previously, concentrations in the range of about 0.001 to 5.0percent by weight, based on the total weight of the elastomericpolyurethane, have been found to be appropriate for adjusting theresistivity of the polymer to within the desired limits.

Higher amounts of the conductivity control agent may be used, however,to control the resistivity of the polyurethane elastomer, the onlylimitation being the desired resistivity of the elastomeric polyurethanefor use as a coating material upon the conductive substrate of thebiasable transfer member.

The conductivity control agent is simply included in the desired amountin the combination of starting materials, most typically as a componentof the hardener composition and covalently bonds to the polymer matrix,i.e., to the backbone and/or a crosslinking and/or a branched portion ofthe polymer during the normal process of elastomer preparation as isexplained more fully below.

The conductivity control agents of the invention are comprised ofethylene glycol or a low molecular weight oligoethylene glycol,specifically diethylene glycol, triethylene glycol or tetraethyleneglycol, complexed with an ionizable ferric halide salt selected from thegroup consisting of ferric fluoride, ferric chloride and ferric bromide.Such complexes can be prepared by dissolving an ionizable ferric halide,such as ferric chloride, and a low molecular weight oligoethyleneglycol, specifically diethylene glycol, triethylene glycol ortetraethylene glycol, in a suitable solvent, such as methanol, forexample, and subsequently evaporating the solvent. The resultantmaterial is believed to be comprised of a complex of the ferric halidewith the ethylene glycol or the low molecular weight oligoethyleneglycol, aforedescribed. In practice, it is advantageous to include anexcess of the oligomer in order to reduce the viscosity of the proposedcomplex. Optionally, the conductivity control agent may be prepared inthe absence of solvent.

As mentioned previously, the conductivity control agent bonds covalentlyto the polymeric matrix or network. This is achieved by reaction of thehydroxyl groups of the conductivity control agent with excess isocyanatepresent in the prepolymer which form urethane linkages in the backboneand/or crosslinking and/or branched portions of the polymer therebyfirmly anchoring the conductivity control agent in the polymericnetwork. This enables the polymer to retain a relatively constant degreeor level of resistivity which will not change substantially (e.g.,decrease) over time during use.

In addition, the conductivity control agents used in the presentinvention for controlling or adjusting the resistivity of thepolyurethane elastomers which form the coatings on the conductivesubstrates of the biasable transfer members of the invention alsosignificantly reduce the sensitivity of the resistivity of thepolyurethane to changes in the relative humidity.

By a significant reduction in the sensitivity of the resistivity tochanges in relative humidity is meant a reduction of its sensitivity ofat least about 80.0 percent. Reductions in relative humidity sensitivityof up to 98 percent have been demonstrated by the method andcompositions of the present invention.

The relative humidity sensitivities of the elastomeric polyurethanesused in the invention for making biasable transfer members by coating aconductive substrate for supporting a uniform bias potential thereonwith at least one coating of the elastomeric polyurethane have beenobtained by measuring the volume resistivity of the polyurethanes at arelative humidity of 0% and a relative humidity of 100%. The ratio ofthe resistivity of a relative humidity of 0% to the resistivity at arelative humidity of 100% is the relative humidity sensitivity. Thisrelative humidity sensitivity also is referred to as the relativehumidity swing. The ratio of the sensitivity at a relative humidity of0% and a relative humidity of 100%, should be about 1 to 10 to provide asuitable biasable transfer member in accordance with the presentinvention. Ideally, the ratio should be 1. As mentioned above, inaddition to the desirability of having a low relative humidity swing,the elastomeric polyurethanes useful for biasable transfer members mustalso have a resistivity of from about 1.0×10⁷ to about 5.0×10¹⁰ ohm cm,and preferably from about 2.0×10⁸ to about 2.0×10¹⁰ ohm cm. In the eventa particular elastomeric polyurethane has a resistivity higher than thedesired resistivity, the resistivity may be adjusted by the inclusion ofa suitable amount of conductivity control agent to adjust theresistivity of the particular polymeric material as describedpreviously.

As mentioned previously, the hardness of the elastomeric polyurethanesof the invention is between about 10 Shore A to about 80 Shore D, andpreferably about 15-100 Shore A. The control of the hardness is withinthe purview of those skilled in the art and the hardness can becontrolled by such parameters as by varying the type and amount ofreactants used and by using various additives such as plasticizers.

In accordance with the invention, there is described the method ofcontrolling the resistivity of a biasable transfer member. There is alsodescribed a method of reducing the sensitivity of the resistivity of theelastomeric polyurethanes to changes in relative humidity by coating aconductive substrate for supporting a uniform bias potential thereonwith at least one layer of an elastomeric polyurethane having aconductivity control agent included therein characterized by beingbonded covalently to the polymeric network or matrix of the elastomer tocontrol resistivity and having a resistivity of from about 1.0×10⁷ toabout 5.0×10¹⁰ ohm cm, and preferably from about 2.0×10⁸ to about2.0×10¹⁰ ohm cm. The coating can be applied to the substrate by anysuitable method or technique known in the art including spraying,casting in molds, affixing sheets of the material to the substratemember by suitable mechanical means or by suitable cement, and the like.

The following examples and comparative tests illustrate more clearly theelastomeric polyurethane materials which may be used in preparing thebiasable transfer members of the present invention and for controllingthe resistivity of the biasable transfer members of the presentinvention, including controlling the sensitivity of the resistivity tochanges in relative humidity although the invention is not to beconstrued as limited in scope thereby

SAMPLE PREPARATION

Slabs of the particular elastomeric polyurethanes to be tested were castin a stainless steel mold in sheets to a thickness of 0.25 inch (0.635cm). Samples of the various cast materials were placed in controlledhumidity chambers for a designated number of days. One set of chamberswas maintained at a relative humidity of 0% and another set of chamberswas maintained at a relative humidity of 100%. A 0% relative humidityenvironment was obtained by suspending the test samples in a sealed jarcontaining 1 inch Drierite at 24° C. A 100% relative humidityenvironment was obtained by suspending the samples over water in asealed jar at 24° C. The samples were suspended in the chambers in sucha way that both sides were available to the atmosphere. In this manner,the samples would have taken up very close to the equilibrium amounts ofwater within 14 days. After 14 days, the volume resistivity of thesamples were measured according to the procedure of ASTM Standard D-257by placing the samples between two soft electrodes of a known surfacearea, applying a 1 kilovolt DC bias from a Trek 610C Cor-A-Trol (highvoltage supply) to one electrode and measuring the current from thesecond electrode using a Kiethly 485 Picoammeter. Values are reported inohm cm.

The resistivities measured at both 0% and 100% relative humidity wererecorded. For the designated examples below, the ratio of theresistivity at 0% relative humidity to the resistivity at 100% relativehumidity was determined. The resulting ratio was designated as the RHsensitivity or RH swing and is reported as RH sensitivity in Table Ibelow where resistivity at 0% and 100% relative humidities is alsodesignated for the various samples tested.

EXAMPLE 1

This example describes the preparation of a conductivity control agentuseful in accordance with the invention which is a diethyleneglycol-ferric chloride complex.

A complex of diethylene glycol and ferric chloride was prepared byslowly adding 162.21 g (1.0 mol) of anhydrous ferric chloride to a 2liter, three-neck round bottom flask equipped with a Teflon bladestirrer and containing 1 liter of dry methanol with 100 ml of drymethanol rinse. The addition process was exothermic and resulted in adark turbid solution. Next, 318.36 g (3.0 mol) of diethylene glycol wereadded to the flask with 100 ml of dry methanol rinse. The resultant hazysolution was stirred for approximately 10 minutes and then filteredthrough diatomaceous earth with more dry methanol wash. The combinedclear filtrate and wash were concentrated in vacuo with steam bathheating to give 475.20 g of a dark syrupy complex (99.09% of theory)characterized by combustion and ICP analysis as diethylene glycolcomplexed with ferric chloride.

Anal. Calcd. for C₁₂ H₃₀ Cl₃ O₉ Fe: C, 29.99; H, 6.29; Cl, 22,13; Fe,11.6; Found: C, 29.94; H, 5.93; Cl, 22.49; Fe, 10.9.

EXAMPLE 2

This example describes the preparation of a crosslinked 40 DurometerShore A hardness elastomeric polyurethane of the invention prepared froma two-component polyurethane commercial mix obtained from Conap Inc.,Olean, N.Y., designated as CONATHANE TU-400 containing the conductivitycontrol agent prepared in accordance with Example 1.

A one-liter glass beaker was charged with 0.45 g of the conductivitycontrol agent prepared in accordance with Example 1. To the beaker wereadded 83.59 g of CONATHANE TU-400 Part B of the mix, a hydroxylterminated polymer based on poly(propylene oxide) and a phenylenediamine chain extender, and the mixture was mechanically stirred at roomtemperature until a solution was obtained. Next, 96.41 g of CONAIHANETU-400 Part A of the mix, i.e., methylene-bis(4-isocyanatocyclohexane)and a hydroxyl-terminated polymer based on poly(propylene oxide) wereadded to the beaker and the mixture was mechanically stirred for fiveminutes. The entrapped air was removed under reduced pressure and themixture was poured into a prepared stainless steel mold which was placedinto an 80° C. hot air oven for three hours. The resulting slab wasremoved from the mold and post cured at 80° C. in a hot air oven forthirteen hours. The slab was then removed from the oven, cooled to roomtemperature and the resistivities of the resultant slab molded to athickness of 0.25 inch (0.635 cm) were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table I,Example 2 below.

Comparative Example 3

This example describes the preparation of the crosslinked polyurethaneelastomer of Example 2 without the conductivity control agent of Example1, as a control, and the resistivity and relative humidity sensitivityof the elastomer as measured in accordance with the aforedescribedprocedure.

A one-liter glass beaker was charged with 83.59 g of CONATHANE TU-400Part B, as defined in Example 2. Next, a solution of 96.41 g ofCONATHANE TU-400 Part A, as defined in Example 2, was added to thebeaker and the resultant mixture was mechanically stirred for fiveminutes at room temperature. The entrapped air was removed under reducedpressure and the mixture was poured into a prepared stainless steel moldwhich was placed into an 80° C. hot air oven for three hours. Theresulting slab was removed from the mold and post cured at 80° C. in ahot air oven for thirteen hours. The slab was then removed from theoven, cooled to room temperature and the resistivities of the resultantslab molded to a thickness of 0.25 inch (0.625 cm) were measured asdescribed above at the two designated relative humidities and therelative humidity sensitivity was determined after an equilibration timeof fourteen days in a relative humidity chamber. The results are shownin Table I, Example 3 below.

EXAMPLE 4

This example describes the preparation of a crosslinked 50 DurometerShore A hardness elastomeric polyurethane of the invention prepared fromfrom a two-component polyurethane commercial mix obtained from ConapInc., Olean, New York, designated as CONATHANE TU-500 containing theconductivity control agent prepared in accordance with Example 1.

To a one-liter glass beaker containing 78.78 g of CONATHANE TU-500 PartB of the mix, a hydroxyl-terminated polymer based on poly(propyleneoxide) and a phenylene diamine chain extender, there was charged 0.5413g of a ferric chloride-diethylene glycol conductivity control agentprepared in accordance with Example 1. The mixture was stirred at roomtemperature until homogeneous. Next, 101.70 g of CONATHANE TU-500 Part Aof the mix, i.e., methylenebis(4-isocyanatocyclohexane) and ahydroxy-terminated polymer based on poly(propylene oxide) were added tothe beaker and the reaction mixture was mechanically stirred at roomtemperature for five minutes. The entrapped air was removed underreduced pressure and the mixture was poured into a prepared stainlesssteel mold which was placed into an 80° C. hot air oven for sixteenhours to cure. The resulting slab was then removed from the oven,removed from the mold, cooled to room temperature and the resistivitiesof the resultant slab molded to a thickness of 0.25 inch (0.635 cm) weremeasured as described above at the two designated relative humiditiesand the relative humidity sensitivity was determined after anequilibration time of fourteen days in a relative humidity chamber. Theresults are shown in Table I, Example 4 below.

COMPARATIVE EXAMPLE 5

This example describes the preparation of the crosslinked polyurethaneelastomer of Example 4 without the conductivity control agent of Example1, as a control, and the resistivity and relative humidity sensitivityof the elastomer as measured in accordance with the aforedescribedprocedure.

A one-liter glass beaker was charged with 78.78 g of CONATHANE TU-500Part B, as defined in Example 4. Next, a solution of 101.70 g ofCONATHANE TU-500 Part A, as defined in Example 4, was added to thebeaker and the resultant mixture was mechanically stirred for fiveminutes at room temperature. The entrapped air was removed under reducedpressure and the mixture was poured into a prepared stainless steel moldwhich was placed into an 80° C. hot air oven for sixteen hours to cure.The resulting slab was then removed from the oven, demolded, cooled toroom temperature and the resistivities of the resultant slab molded to athickness of 0.25 inch (0.625 cm) were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table I,Example 5 below.

EXAMPLE 6

This example describes the preparation of a crosslinked 90 DurometerShore A hardness elastomeric polyurethane of the invention prepared froma two-component polyurethane commercial mix obtained from Conap Inc.,Olean, N.Y., designated as CONATHANE TU-900 containing the conductivitycontrol agent prepared in accordance with Example 1.

To a one-liter glass beaker containing 48.57 g of CONATHANE TU-900 PartB of the mix, a hydroxyl-terminated polymer based on poly(propyleneoxide) and a phenylene diamine chain extender, there were charged 3.6 gof the ferric chloride-diethylene glycol conductivity control agentprepared in accordance with Example 1. The mixture was stirred at roomtemperature until homogeneous. Next, 127.5 g of CONATHANE TU-900 Part Aof the mix, i.e., methylenebis(4-isocyantocyclohexane) and ahydroxy-terminated polymer based on poly(propylene oxide) were added tothe beaker and the reaction mixture was mechanically stirred at roomtemperature for five minutes. The entrapped air was removed underreduced pressure and the mixture was poured into a prepared stainlesssteel mold which was placed into an 80° C. hot air oven for sixteenhours to cure. The resulting slab was then removed from the oven,demolded, cooled to room temperature and the resistivities of theresultant slab molded to a thickness of 0.25 inch (0.635 cm) weremeasured as described above at the two designed relative humidities andthe relative humidity sensitivity was determined after an equilibrationtime of fourteen days in a relative humidity chamber. The results areshown in Table I, Example 6, below.

COMPARATIVE EXAMPLE 7

This example describes the preparation of the crosslinked polyurethaneelastomer of Example 6 without the conductivity control agent of Example1, as a control, and the resistivity and relative humidity sensitivityof the elastomer as measured in accordance with the aforedescribedprocedure.

A one-liter glass beaker was charged with 48.57 g of CONATHANE TU-900Part B, as defined in Example 6. Next, a solution of 127.5 g ofCONATHANE TU-900 Part A, as defined in Example 6, was added to thebeaker and the resultant mixture was mechanically stirred for fiveminutes at room temperature. The entrapped air was removed under reducedpressure and the mixture was poured into a prepared stainless steel moldwhich was placed into an 80° C. hot air oven for sixteen hours. Theresulting slab was then removed from the oven, demolded, cooled to roomtemperature, and the resistivities of the resultant slab molded to athickness of 0.25 inch (0.625 cm) were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table I,Example 7 below.

EXAMPLE 8

This example describes the preparation of a crosslinked 90 DurometerShore A hardness elastomeric polyurethane of the invention containingthe conductivity control agent of Example 1.

To a one-liter glass beaker containing 171.0 g of a toluenediisocyanate/polytetramethylene ether glycol prepolymer obtained fromUniroyal Co. as Adiprene L100, there were added 9.0 g (0.042 mol) ofdi(methylthio)-2,4-toluenediamine, an aromatic diamine sold by andobtained from Ethyl Corporation under the trade name Ethacure 300, and0.45 g of the ferric chloride-diethylene glycol conductivity controlagent prepared as described in Example 1. The reaction was stirred atroom temperature, under nitrogen, for five minutes, degassed and pouredinto a heated stainless steel mold. The polymer was cured for sixteenhours at 80° C. and demolded. The slab was then cooled to roomtemperature and the resistivities of the resultant slab molded to athickness of 0.25 inch (0.635 cm) were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table I,Example 8 below.

COMPARATIVE EXAMPLE 9

This example describes the preparation of the crosslinked polyurethaneelastomer of Example 8 without the conductivity control agent of Example1, as a control, and the resistivity and relative humidity sensitivityof the elastomer as measured in accordance with the aforedescribedprocedure.

To a one-liter glass beaker containing 171.0 g of a toluenediisocyanate/polytetramethylene ether glycol prepolymer obtained fromUniroyal Co. as Adiprene L100, there were added 9.0 g (0.042 mol) ofdi(methylthio)-2,4-toluenediamine, an aromatic diamine sold by andobtained from Ethyl Corporation as Ethacure 300, as defined in previousExample 8. The reaction was stirred at room temperature, under nitrogen,for five minutes, degassed and poured into a heated stainless steelmold. The polymer was cured for sixteen hours at 80° C. and demolded.The slab was then cooled to room temperature and the resistivities ofthe resultant slab molded to a thickness of 0.25 inch (0.625 cm) weremeasured as described above at the two designated relative humiditiesand the relative . humidity sensitivity was determined after anequilibration time of fourteen days in a relative humidity chamber. Theresults are shown in Table I, Example 9 below.

EXAMPLE 10

This example describes the preparation of a crosslinked 55 DurometerShore A hardness elastomeric polyurethane of the invention prepared froma two-component polyurethane commercial mix obtained from WinfieldIndustries, Inc., Buffalo, N.Y., designated as Winthane W643 containingthe conductivity control agent prepared in accordance with Example 1.

To a one-liter glass beaker containing 11.13 g of Winthane W643 Part Bof the mix, there was charged 0.63 g of the ferric chloride-diethyleneglycol conductivity control agent prepared in accordance with Example 1.The mixture was stirred at room temperature until homogeneous. Next,169.0 g of Winthane W643 Part A of the mix were added to the beaker andthe reaction mixture was mechanically stirred at room temperature forthree minutes. The entrapped air was removed under reduced pressure andthe mixture was poured into a prepared stainless steel mold which wasplaced into an 80° C. hot air oven for sixteen hours to cure. Theresulting slab was then removed from the oven, demolded, cooled to roomtemperature and the resistivities of the resultant slab molded to athickness of 0.25 inch (0.635 cm) were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table I,Example 10 below.

COMPARATIVE EXAMPLE 11

This example describes the preparation of the crosslinked polyurethaneelastomer of Example 10 without the conductivity control agent ofExample 1, as a control, and the resistivity and relative humiditysensitivity of the elastomer as measured in accordance with theaforedescribed procedure.

A one-liter glass beaker was charged with 11.13 g of Winthane W643 PartB. Next, a solution of 169.0 g of Winthane W643 Part A of the mix wereadded to the beaker and the resultant mixture was mechanically stirredfor three minutes at room temperature. The entrapped air was removedunder reduced pressure and the mixture was poured into a preparedstainless steel mold which was placed into an 80° C. hot air oven forsixteen hours. The resulting slab was then removed from the oven,demolded, cooled to room temperature and the resistivities of theresultant slab molded to a thickness of 0.25 inch (0.625 cm) weremeasured as described above at the two designated relative humiditiesand the relative humidity sensitivity was determined after anequilibration time of fourteen days in a relative humidity chamber. Theresults are shown in Table I, Example 11 below.

EXAMPLE 12

This example describes the preparation of a crosslinked 48 DurometerShore A hardness elastomeric polyurethane of the invention containingthe conductivity control agent of Example 1.

To a 500 ml resin kettle containing 98.63 g (0.098 mol) of Terathane1000, a poly(tetramethylene ether glycol) available from E.I. DuPont deNemours Company, (Mn=1000) and 0.36 g of the ferric chloride-diethyleneglycol conductivity control agent prepared in accordance with Example 1,there were added, with stirring, 65.70 g (0.25 mol) ofmethylenebis(4-isocyanatocyclohexane) obtained commercially from MobayCorporation under the trade name Desmodur W. The stirred reactionmixture was heated at 80° C. under nitrogen for seventy minutes. Next,98.63 g (0.098 mol) of poly(tetramethylene ether glycol) were addedalong with 4.0 g (0.0225 mol) of an isomeric mixture ofdiethyltoluenedimaine obtained commercially as Ethacure 100 from EthylCorporation. The reaction was stirred under nitrogen at 80° C. for fiveminutes, degassed under reduced pressure and poured into a stainlesssteel mold. The polymer was cured in an 80° C. oven for sixteen hours.The slab was then removed from the oven, demolded, cooled to roomtemperature and the resistivities of the resultant slab molded to athickness of 0.25 inch (0.625 cm) were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table I,Example 12 below.

EXAMPLE 13

This example describes the preparation of a crosslinked 22 DurometerShore A hardness elastomeric polyurethane of the invention containingthe conductivity control agent of Example 1.

To a 500 ml resin kettle containing 195.0 g (0.098 mol) poly(propyleneglycol) obtained commercially from Dow Chemicals under the trade namePolyglycol P-2000 (M_(n) =2000) and 65.79 g (0.25 mol) ofmethylenebis(4-isocyanatocyclohexane), obtained commercially from MobayCorporation under the trade name Desmodur W, there was added, withstirring, 0.40 g of the ferric chloride-diethylene glycol conductivitycontrol agent prepared in accordance with Example 1. The reactionmixture was stirred at 80° C. under nitrogen for one hour. Next, 195.0 g(0.098 mol) of the poly(propylene glycol) aforedescribed and 4.90 g(0.0275 mol) of an isomeric mixture of diethyltoluenediamine, obtainedcommercially as Ethacure 100 from Ethyl Corporation, were added to thereaction mixture. The reaction mixture was stirred for five minutes,under nitrogen, degassed under reduced pressure and poured into astainless steel mold. The polymer was cured in an 80° C. oven forsixteen hours. The slab was then removed from the oven, demolded, cooledto room temperature and the resitivities of the resultant slab molded toa thickness of 0.25 inch (0.635) were measured as described above at thetwo designated relative humidities and the relative humidity sensitivitywas determined after an equilibration time of fourteen days in arelative humidity chamber. The results are shown in Table I, Example 13below.

EXAMPLE 14

This example describes the preparation of a crosslinked 50 DurometerShore A hardness elastomeric polyurethane of the invention containingthe conductivity control agent of Example 1.

To a 500 ml resin kettle containing 121.89 g (0.098)poly(caprolactone)diol; M_(n) =1250 obtained commercially from AldrichChemical Co., Inc., and 65.79 g, (0.25mol) ofmethylenebis(4-isocyanatocylcohexane), obtained commercially from MobayCorporation under the trade name Desmodur W, there was added, withstirring, 0.40 g of the ferric chloride-diethylene glycol conductivitycontrol agent prepared in accordance with Example 1. The reaction wasstirred, under nitrogen, at 80° C. for seventy minutes. Next. 121.89 g(0.098 mol) of poly(caprolactone)diol and 4.90 g (0.0275 mol) of anisomeric mixture of diethyltoluenediamine, obtained commercially asEthacure 100 from Ethyl Corporation, were added to the reaction mixture.The reaction mixture was stirred, under nitrogen, for five minutes,degassed under reduced pressure and poured into a stainless steel mold.The polymer was cured in an 80° C. oven for sixteen hours. The slab wasthen removed from the oven, demolded, cooled to room temperature and theresistivities of the resultant slab molded to a thickness of 0.25 inch(0.635 cm) were measured as described above at the two designatedrelative humidities and the relative humidity sensitivity was determinedafter an equilibration time of fourteen days in a relative humiditychamber. The results are shown in Table I, Example 14 below.

EXAMPLE 15

This Example describes the preparation of a crosslinked elastomericpolyurethane outside the scope of the invention to show that thepolyurethane elastomers of the present invention are superior topolyurethane elastomers of the prior art with respect to moisturestability. The example shows the preparation of a polyurethane elastomermade from the two-part CONATHANE TU-500 commercial polyurethane mixdescribed above except that 0.14 weight percent of the conductivitycontrol agent described in Example 9 of U.S. Pat. No. 5,011,739, i.e., acomplex of lithium iodide and tetramethylene glycol was added to Part Bof the polyurethane mix prior to the addition of Part B to Part A of themix.

A one-liter glass beaker was charged with 0.21 of the lithiumiodide-tetraethylene glycol conductivity control agent prepared asfollows. To a 500 ml single-neck, round-bottom flask equipped with amagnetic stirrer containing 11.24 g (0.084 mol) of lithium iodide and100 ml of methanol, there was added 16.31 (0.084 mol) of tetraethyleneglycol. The solution was stirred for 10 minutes. The methanol wasremoved under reduced pressure leaving a solid material characterized bycombustion analysis as tetraethylene glycol complexed with lithiumiodide. The beaker was then placed into a hot air oven and heated at150° C. until the lithium iodide-tetraethylene glycol conductivitycontrol agent melted. To the beaker were added 65.90 g of CONATHANETU-500 Part B of the mix, a hydroxy-terminated polymer based onpoly(propylene oxide) and a phenylene diamine chain extender, and themixture was mechanically stirred while heated until a solution wasobtained. Next, 83.88 g of CONATHANE TU-500 Part A of the mix, i.e.,methylenebis(4-isocyanatocyclohexane) and a hydroxyl-terminated polymerbased on poly(propylene oxide) were added to the beaker and the mixturewas mechanically stirred for 5 minutes. The entrapped air was removedunder reduced pressure and the mixture was poured into a preparedstainless steel mold which was placed into an 80° C. hot air oven for 3hours. The resulting slab was removed from the mold and post cured at80° C. in a hot air oven for 13 hours. The slab was then cooled to roomtemperature and the resistivities were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of 14 days in arelative humidity chamber. The results are shown in Table I, Example 15below.

                  TABLE I                                                         ______________________________________                                        Humidity Sensitivities of the Polyurethane                                    Elastomers of Examples 2-15                                                          Resistivity at                                                                Designated Relative                                                           Humidity       Time    RH                                              Examples 0%        100%       (Days)                                                                              Sensitivity                               ______________________________________                                        Example 2                                                                              3.58 × 10.sup.8                                                                   2.73 × 10.sup.8                                                                    14    1.31                                      Comparative                                                                            1.16 × 10.sup.12                                                                  1.63 × 10.sup.10                                                                   14    71.17                                     Example 3                                                                     Example 4                                                                              8.96 × 10.sup.8                                                                   1.03 × 10.sup.9                                                                    14    0.87                                      Comparative                                                                            9.79 × 10.sup.11                                                                  4.81 × 10.sup.10                                                                   14    20.35                                     Example 5                                                                     Example 6                                                                              1.60 × 10.sup.8                                                                   9.63 × 10.sup.7                                                                    14    1.66                                      Comparative                                                                            7.33 × 10.sup.12                                                                  1.23 × 10.sup.11                                                                   14    59.59                                     Example 7                                                                     Example 8                                                                              1.36 × 10.sup.8                                                                   1.19 × 10.sup.8                                                                    14    1.14                                      Comparative                                                                            2.27 × 10.sup.11                                                                  2.90 × 10.sup.10                                                                   14    7.83                                      Example 9                                                                     Example 10                                                                             5.17 × 10.sup.8                                                                   1.01 × 10.sup.8                                                                    14    5.12                                      Comparative                                                                            7.76 × 10.sup.11                                                                  1.23 × 10.sup.10                                                                   14    63.09                                     Example 11                                                                    Example 12                                                                             2.62 × 10.sup.9                                                                   2.37 × 10.sup. 9                                                                   14    1.11                                      Example 13                                                                             3.56 × 10.sup.9                                                                   1.58 × 10.sup.9                                                                    14    2.25                                      Example 14                                                                             2.93 × 10.sup.9                                                                   1.09 × 10.sup.9                                                                    14    2.7                                       Example 15                                                                             9.73 × 10.sup.9                                                                   7.04 × 10.sup.9                                                                    14    1.38                                      ______________________________________                                    

The reduction in resistivity by the use of the conductivity controlagents of the invention, as well as the resulting reduction in RHsensitivity, is clearly shown in Table I by comparing the resistivitiesand the RH sensitivities of the polyurethane elastomers of ComparativeExamples 3, 5, 7, 9 and 11, without a conductivity control agent of thepresent invention, to the resistivities and the RH sensitivities of thepolyurethane elastomers of Examples 2, 4, 6, 8 and 10, respectively,consisting of the same polyurethane elastomers of Examples 3, 5, 7, 9and 11, but containing a conductivity control agent of the presentinvention. Further, a comparison of the relative humidity sensitivityand resistivity of the polyurethane elastomer of Example 15 containingthe lithium iodide-tetramethylene glycol conductivity control agent ofExample 9 of U.S. Pat. No. 5,011,739, with the relative humiditysensitivity of the polyurethane elastomer of Example 4 consisting of thesame polyurethane elastomer but containing a conductivity control agentof the present invention, clearly shows the substantial reduction in RHsensitivity when the conductivity control agent of the present inventionis used to control the resistivity of the polyurethane elastomer ascompared to the alkali metal salt-oligoethylene glycol complexconductivity control agent of the prior art.

EXAMPLE 16

This example describes the preparation of a linear, non-crosslinked 62Durometer Shore A hardness thermoplastic polyurethane containing theconductivity control agent prepared in accordance with Example 1.

A mixture of 140.0 g (0.14 mol) of commercially availablepoly(tetramethylene ether glycol) obtained under the trade nameTerathane 1000 from E.I. DuPont de Nemours Company, (M_(n) =1,000) and0.16 g of dibutyltin dilaurate was dried in a 3-neck, 500 ml roundbottom flask equipped with a Teflon blade stirrer at room temperature invacuo (approximately 1.0 mm) for approximately 30 minutes. Next, 52.47 g(0.20 mol) of methylenebis(4-isocyanatocyclohexane) obtainedcommercially under the trade name Desmodur W from Mobay Corporation wereadded to the flask and the reaction mixture was heated in an 80° C. bathunder nitrogen for 70 minutes to form the isocyanate terminatedprepolymer. An isomeric mixture of 7.84 g (0.044 mol) ofdiethyltoluenediamine, obtained commercially under the trade nameEthacure 100 from Ethyl Corporation, was then added to the flask alongwith 2.56 g of the ferric chloride-diethylene glycol conductivitycontrol agent prepared in accordance with the procedure of Example 1.The mixture was stirred for approximately 5 minutes in an 80° C. bath,degassed under reduced pressure and poured into a stainless steel mold.The polymer was cured in an 80° C. oven for 20 hours, demolded, cooledto room temperature and the resistivities of the resultant slab moldedto a thickness of 0.25 inch (0.625 cm) were measured as described aboveat the two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table II,Example 16 below.

COMPARATIVE EXAMPLE 17

This example describes the preparation of the linear, non-crosslinkedpolyurethane elastomer of Example 16 without the conductivity controlagent of Example 1, as a control, and the resistivity and relativehumidity sensitivity of the elastomer as measured in accordance with theaforedescribed procedure.

Commercially available poly(tetramethylene ether glycol), 140.0 g (0.14mol), obtained under the trade name Terathane 1000 from E.I. DuPont deNemours Company, (M_(n) =1,000) was dried in a three-neck, 500 ml roundbottom flask equipped with a Teflon blade stirrer at room temperature invacuo (approximately 1.0 mm) for approximately 30 minutes. Next, 52.47 g(0.20 mol) of methylenebis(4-isocyanatocyclohexane), obtainedcommercially under the trade name Desmodur W from Mobay Corporation,along with 0.16 g of dibutyltin dilaurate were added to the flask andthe reaction mixture was heated in an 80° C. bath under nitrogen forseventy minutes to form the isocyanate terminated prepolymer. Anisomeric mixture of 7.84 g (0.044 mol) of diethyltoluenediamine obtainedcommercially under the trade name Ethacure 100 from Ethyl Corporation,was then added to the flask along with 1.70 g (0.016 mol) of diethyleneglycol in place of the conductivity control agent of Example 1 to insurethat a polyurethane elastomer of the same stoichiometric balance as thatproduced in Example 16, but devoid of any conductivity control agent ofthe present invention, was obtained. The mixture was stirred forapproximately 5 minutes in an 80° C. bath, degassed under reducedpressure and poured into a stainless steel mold. The polymer was curedin an 80° C. oven for 20 hours, demolded, cooled to room temperature andthe resistivities of the resultant slab molded to a thickness of 0.25inch (0.635 cm) were measured as described above at the two designatedrelative humidities and the relative humidity sensitivity was determinedafter an equilibration time of fourteen days in a relatively humiditychamber. The results are shown in Table II, Example 17 below.

EXAMPLE 18

This example describes the preparation of a linear, non-crosslinked 50Durometer Shore A hardness thermoplastic polyurethane containing theconductivity control agent prepared in accordance with Example 1.

In a 3-neck, 500 ml round bottom flask equipped with a Teflon bladestirrer, 140.0 g (0.14 mol) of poly(propylene glycol); M_(n) =1000, wasdried at room temperature in vacuo (approximately 1.0 mm) forapproximately 30 minutes. Next, 52.47 g (0.20 mol) ofmethylenebis(4-isocyanato-cyclohexane), obtained commercially under thetrade name Desmodur W from Mobay Corporation, along with 0.16 g ofdibutyltin dilaurate, were added to the flask and the reaction mixturewas heated in an 80° C. bath under nitrogen for 70 minutes to from theisocyanate terminated prepolymer. An isomeric mixture of 7.84 g (0.044mol) of diethyltoluenediamine, obtained commercially under the tradename Ethacure 100 from Ethyl Corporation, was added along with 2.56 g ofthe ferric chloride-diethylene glycol conductivity control agentprepared in accordance with the procedure of Example 1. The mixture wasstirred for approximately 5 minutes in an 80° C. bath, degassed underreduced pressure and poured into a stainless steel mold. The polymer wascured in an 80° C. oven for 16 hours, demolded, cooled to roomtemperature and the resistivities of the resultant slab molded to athickness of 0.25 inch (0.635 cm) were measured as described above atthe two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table II,Example 18 below.

EXAMPLE 19

This example describes the preparation of a linear, non-crosslinked 80Durometer Shore A hardness thermoplastic polyurethane containing theconductivity control agent prepared in accordance with Example 1.

In a 3-neck, 500 ml round-bottom flask equipped with a Teflon bladestirrer, 140.0 g (0.215 mol) of commercially availablepoly(tetramethylene ether glycol), obtained under the trade nameTerathane 650 from E. I. DuPont de Nemours Company, (M_(n) =650) wasdried at room temperature in vacuo (approximately 1.0 mm) forapproximately 30 minutes. Next, 80.725 g (0.308 mol) ofmethylenebis(4-isocyanatocyclohexane), obtained commercially under thetrade name Desmodur W from Mobay Corporation, along with 0.246 g ofdibutyltin dilaurate, were added to the flask and the reaction mixturewas heated in an 80° C. bath under nitrogen for 70 minutes to form theisocyanate terminated prepolymer. An isomeric mixture of 14.26 g (0.080mol) of an isomeric mixture of diethyltoluenediamine, obtainedcommercially under the trade name Ethacure 100 from Ethyl Corporation,was added along with 1.97 g of the ferric chloride-diethylene glycolconductivity control agent prepared in accordance with the procedure ofExample 1. The mixture was stirred for approximately 5 minutes in an 80°C. bath, degassed under reduced pressure and poured into a stainlesssteel mold. The polymer was cured in an 80° C. oven for 16.5 hours,demolded, cooled to room temperature and the resistivities of theresultant slab molded to a thickness of 0.25 inch (0.635 cm) weremeasured as described above at the two designated relative humiditiesand the relative humidity sensitivity was determined after anequilibration time of fourteen days in a relative humidity chamber. Theresults are shown in Table II, Example 19 below.

COMPARATIVE EXAMPLE 20

This example describes the preparation of the linear, non-crosslinkedpolyurethane elastomer of Example 19 without the conductivity controlagent of Example 1, as a control, and the resistivity and relativehumidity sensitivity of the elastomer as measured in accordance with theaforedescribed procedure.

In a three-neck, 500 ml round-bottom flask equipped with a Teflon bladestirrer, 140.0 g (0.215 mol) of commercially availablepoly(tetramethylene ether glycol) obtained under the trade nameTerathane 650 from E. I. DuPont de Nemours Company (M_(n) =650) wasdried at room temperature in vacuo (approximately 1.0 mm) forapproximately 30 minutes. Next, 80.725 g (0.308 mol) ofmethylenebis(4-isocyanatocyclohexane), obtained commercially under thetrade name Desmodur W from Mobay Corporation, along with 0.246 g ofdibutyltin dilaurate, were added to the flask and the reaction mixturewas heated in an 80° C. bath under nitrogen for 70 minutes to form theisocyanate terminated prepolymer. An isomeric mixture of 14.26 g (0.080mol) of diethyltoluenediamine, obtained commercially under the tradename Ethacure 100 from Ethyl Corporation, was then added to the flask,along with 1.31 g (0.0123 mol) of diethylene glycol in place of theconductivity control agent of Example 1 to insure that a polyurethaneelastomer of the same stoichiometric balance as that produced in Example19, but devoid of any conductivity control agent of the presentinvention, was obtained. The mixture was stirred for approximately 5minutes in an 80° C. bath, degassed under reduced pressure and pouredinto a stainless steel mold. The polymer was cured in an 80° C. oven for16.5 hours, demolded, cooled to room temperature and the resistivitiesof the resultant slab molded to a thickness of 0.25 inch (0.635 cm) weremeasured as described above at the two designated relative humiditiesand the relative humidity sensitivity was determined after anequilibration time of fourteen days in a relative humidity chamber. Theresults are shown in Table II, Example 20 below.

EXAMPLE 21

This example describes the preparation of a linear, non-crosslinked 88Durometer Shore A hardness thermoplastic polyurethane containing theconductivity control agent prepared in accordance with Example 1.

In a 3-neck, 500 ml round-bottom flask equipped with a Teflon bladestirrer, 97.50 g (0.15 mol) of commercially availablepoly(tetramethylene ether glycol) obtained under the trade nameTerathane 650 from E. I. DuPont de Nemours Company (M_(n) =650) wasdried at room temperature in vacuo (approximately 1.0 mm) forapproximately 30 minutes. Next, 65.59 g (0.25 mol) ofmethylenebis(4-isocyanatocyclohexane), obtained commercially under thetrade name Desmodur W from Mobay Corporation, along with 0.20 gdibutyltin dilaurate, were added to the flask and the reaction mixturewas heated in an 80° C. bath under nitrogen for 70 minutes to form theisocyanate terminated prepolymer. An isomeric mixture of 16.94 g (0.095mole) of diethyltoluenediamine, obtained commercially under the tradename Ethacure 100 from Ethyl Corporation, was added along with 0.80 g ofthe ferric chloride-diethylene glycol conductivity control agentprepared in accordance with the procedure of Example 1. The mixture wasstirred for approximately 5 minutes in an 80° C. bath, degassed underreduced pressure and poured into a stainless steel mold. The polymer wascured in an 80° C. oven for 3.3 hours, demolded and post cured in an 80°C. oven for 16.5 hours, cooled to room temperature and the resistivitiesof the resultant slab molded to a thickness of 0.25 inch (0.635 cm) weremeasured as described above at the two designated relative humiditiesand the relative humidity sensitivity was determined after anequilibration time of fourteen days in a relative humidity chamber. Allresults are shown in Table II, Example 21 below.

EXAMPLE 22

This example describes the preparation of a linear, non-crosslinked 49Durometer Shore A hardness thermoplastic polyurethane containing theconductivity control agent prepared in accordance with Example 1.

In a 3-neck, 500 ml round-bottom flask equipped with a Teflon bladestirrer, 175.0 g (0.14 mol) of poly(caprolactone)diol; (M_(n) =1250) wasdried at room temperature in vacuo (approximately 1.0 mm) forapproximately 30 minutes. Next, 52.47 g (0.20 mol) ofmethylenebis(4-isocyanatocyclohexane), obtained commercially under thetrade name Desmodur W from Mobay Corporation, along with 0.16 g ofdibutyltin dilaurate, were added to the flask and the reaction mixturewas heated in an 80° C. bath under nitrogen for 70 minutes to form theisocyanate terminated prepolymer. An isomeric mixture of 7.84 g (0.044mol) of diethyltoluenediamine, obtained commercially under the tradename Ethacure 100 from Ethyl Corporation, was then added to the flaskalong with 2.56 g of the ferric chloride-diethylene glycol conductivitycontrol agent prepared in accordance with the procedure of Example 1.The mixture was stirred for approximately 5 minutes in an 80° C. bath,degassed under reduced pressure and poured into a stainless steel mold.The polymer was cured in an 80° C. oven for 16 hours, demolded, cooledto room temperature and the resistivities of the resultant slab moldedto a thickness of 0.25 inch (0.635 cm) were measured as described aboveat the two designated relative humidities and the relative humiditysensitivity was determined after an equilibration time of fourteen daysin a relative humidity chamber. The results are shown in Table II,Example 22 below.

EXAMPLE 23

This example describes the preparation of a linear, non-crosslinked 78Durometer Shore A hardness thermoplastic polyurethane containing theconductivity control agent prepared in accordance with Example 1.

In a 3-neck, 1000 ml round-bottom flask equipped with a Teflon bladestirrer, 341.25 g (0.525 mol) of commercially availablepoly(tetramethylene ether glycol), obtained under the trade nameTerathane 650 from E. I. DuPont de Nemours Company (M_(n) =650) wasdried at room temperature in vacuo (approximately 1.0 mm) forapproximately 30 minutes. Next, 196.76 g (0.75 mol) ofmethylenebis(4-isocyanatocyclohexane), obtained commercially under thetrade name Desmodur W from Mobay Corporation, along with 0.60 g ofdibutyltin dilaurate, were added to the flask and the reaction mixturewas heated in an 80° C. bath under nitrogen for 70 minutes to form theisocyanate terminated prepolymer. An isomeric mixture of 34.76 g (0.195mol) of diethyltoluenediamine, obtained commercially under the tradename Ethacure 100 from Ethyl Corporation, was added to the flask alongwith 4.81 g of the ferric chloride-diethylene glycol conductivitycontrol agent prepared in accordance with the procedure of Example 1.The mixture was stirred for approximately 5 minutes in an 80° C. bath,degassed under reduced pressure, and poured into a stainless steel mold.The polymer was cured in an 80° C. oven for 3.0 hours, demolded, postcured at 80° C. for 18 hours, cooled to room temperature and theresistivities of the resultant slab molded to a thickness of 0.25 inch(0.635 cm) were measured as described above at the two designatedrelative humidities and the relative humidity sensitivity was determinedafter an equilibration time of fourteen days in a relative humiditychamber. The results are shown in Table II, Example 23 below.

EXAMPLE 24

This example describes the preparation of a linear, non-crosslinked 57Durometer Shore A hardness thermoplastic polyurethane containing theconductivity control agent prepared in accordance with Example 1, butprepared in the absence of a catalyst such as previously used dibutyltindilaurate to show that such a catalyst is not required in thepreparation of the polyurethane elastomers of the present invention.However, it is believed and would be expected that the conductivitycontrol agent itself would exert a catalytic effect on thepolymerization reaction due to the presence of ferric halide in theconductivity control agent which is known in and of itself to behave asa polymerization catalyst in the synthesis of polyurethane elastomers.Also in this example, the conductivity control agent is added to thepolyisocyanate prepolymer instead of the hardening mixture todemonstrate that the conductivity control agents used in preparing thepolyurethane elastomers of the present invention can be added to theprepolymer instead of the hardener mixture, if desired.

A mixture of 140.0 g (0.14 mol) of commercially availablepoly(tetramethylene ether glycol), obtained under the trade nameTerathane 1000 from E. I. DuPont de Nemours Company, (M_(n) =1000) and2.56 g of the ferric chloride-diethylene glycol conductivity controlagent prepared in accordance with the procedure of Example 1 was driedin a three-neck, 500 ml round bottom flask equipped with a Teflon bladestirrer at room temperature in vacuo (approximately 1.0 mm) for about 30minutes. Next, 52.47 g (0.20 mol) ofmethylenebis(4-isocyanatecyclohexane), obtained commercially under thetrade name Desmodur W from Mobay Corporation, were added to the flaskand the reaction mixture was heated in an 80° C. bath under nitrogen forseventy minutes to form the isocyanate terminated propolymer. Anisomeric mixture of 7.84 g (0.044 mol) of diethyltoluenediamine,obtained commercially under the trade name Ethacure 100 from EthylCorporation, was added to the flask. The mixture was stirred forapproximately 5 minutes in an 80° C. bath, degassed under reducedpressure and poured into a stainless steel mold. The polymer was curedin an 80° C. bath for 16 hours, demolded, cooled to room temperature andthe resistivities of the resultant slab molded to a thickness of 0.25inch (0.635 cm) were measured as described above at the two designatedrelative humidities and the relative humidity sensitivity was determinedafter an equilibration time of fourteen days in a relative humiditychamber. The results are shown in Table II, Example 24 below.

                  TABLE II                                                        ______________________________________                                        Humidity Sensitivities of the Polyurethane                                    Elastomers of Examples 16-24                                                         Resistivity at                                                                Designated Relative                                                           Humidity       Time    RH                                              Examples 0%        100%       (Days)                                                                              Sensitivity                               ______________________________________                                        Example 16                                                                             7.41 × 10.sup.7                                                                   3.60 × 10.sup.7                                                                    14    2.06                                      Comparative                                                                            5.90 × 10.sup.12                                                                  2.22 × 10.sup.11                                                                   14    26.58                                     Example 17                                                                    Example 18                                                                             2.41 × 10.sup.8                                                                   9.42 × 10.sup.7                                                                    14    2.56                                      Example 19                                                                             7.37 × 10.sup.9                                                                   6.81 × 10.sup.9                                                                    14    1.08                                      Comparative                                                                            1.02 × 10.sup.13                                                                  1.46 × 10.sup.12                                                                   14    6.99                                      Example 20                                                                    Example 21                                                                             1.35 × 10.sup.10                                                                  1.61 × 10.sup.10                                                                   14    0.84                                      Example 22                                                                             4.31 × 10.sup.8                                                                   1.10 × 10.sup.8                                                                    14    3.92                                      Example 23                                                                             2.15 × 10.sup.9                                                                   1.31 × 10.sup.9                                                                    14    1.64                                      Example 24                                                                             8.22 × 10.sup.7                                                                   3.45 × 10.sup.7                                                                    14    2.38                                      ______________________________________                                    

The reduction in resistivity by the use of the conductivity controlagents of the invention in linear, non-crosslinked thermoplasticpolyurethane elastomers, as well as the resulting reduction in RHsensitivity, is clearly shown in Table II by comparing the resistivitiesand the RH sensitivities of the polyurethane elastomers of ComparativeExamples 17 and 20, without a conductivity control agent of the presentinvention, to the resistivities and the RH sensitivities of thepolyurethane elastomers of Examples 16 and 19, respectively, consistingof the same polyurethane elastomers of Examples 17 and 20, butcontaining a conductivity control agent of the present invention.Further, Example 24 shows that polyurethane elastomers of the presentinvention can be prepared in the absence of a catalyst and still possessthe resistivities and RH sensitivities desired of the polyurethaneelastomers of the present invention.

The polyurethane elastomers are capable of being made into shapedarticles such as transfer rollers and belts in which the resistivity canbe maintained at from about 1.0×10⁷ to about 5.0×10¹⁰ ohm cm. Suchshaped articles exhibit toughness, high elongation, high tensilestrength, high tear strength and excellent abrasion resistance. Theshaped articles can be designed to have a hardness ranging from 10 ShoreA to about 80 Shore D. For use in making electrically biasable transferrollers and belts, a Shore hardness of about 15-100 Shore A Durometersis preferred.

Method of Making Transfer Rollers

Transfer rollers can be made from any one of a number of commerciallyavailable polyurethane two-component mixes to which a conductivitycontrol agent of the invention is added. Examples include CONATHANETU-400, CONATHANE TU-500 and CONATHANE TU-900 to which a polyolconductivity control agent of the present invention, for example, can beadded at between about 0.001 and 5.0% by weight of the total weight ofthe hardener composition of Part B of the mix. This results in a rollerresistivity from about 1.0×10⁷ to about 5.0×10¹⁰ ohm cm. In general, thepolyurethanes used are the two-component types comprising A and B. PartA is the isocyanate prepolymer. Part B is the hardener. The conductivitycontrol agent typically is added to Part B of the mix. The preparationshown below is typical for a roller requiring approximately one liter ofpolyurethane and 0.13% conductivity control agent to make a roller witha resistivity of 2.0×10⁸ ohm cm.

EXAMPLE 25

Preparation of a 10 Durometer Shore A Hardness Polyurethane AntistaticRoller

To a 500 ml resin kettle containing 116.25 g (0.058 mol) ofpoly(propylene glycol), M_(n) =2000, there was added, with stirring,0.36 g of the ferric chloride-diethylene glycol conductivity controlagent prepared according to the procedure described in Example 1. Themixture was stirred until homogenous. Next, 39.47 g (0.15 mol) ofmethylenebis(4-isocyanatocyclohexane), obtained commercially from MobayCorporation under the trade name Desmodur W, were added to the flask andthe reaction mixture was stirred at 80° C. for seventy minutes.Following this, 116.25 g (0.058 mol) poly(propylene glycol) and 2.94 g(0.017 mol) of an isomeric mixture of diethyltoluenediamine, obtainedcommercially as Ethacure 100 from Ethyl Corporation, were added to thereaction mixture and the reaction mixture was stirred for five minutes,under nitrogen, degassed under reduced pressure, poured into acylindrical roller mold in the shape of a cylinder containing a centered0.25 inch shaft and cured at 80° C. in an oven for sixteen hours. Themold and casting were then cooled to room temperature after which thecasting was removed from the mold.

The dimensions of the conductive roller are dictated by the design ofthe copy equipment into which the rollers or belts are to beincorporated.

Although Applicants have referred to the biasable member coatingmaterials of the invention throughout as polyurethane materials, it isto be understood that in the strictest sense, when a polyamine ispresent in the hardening composition, the resultant elastomeric materialis comprised of a polyurethane/polyurea elastomer.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

We claim:
 1. A member for electrically cooperating with a conductivesupport surface to attract charged toner particles from the surfacetowards the member comprising a conductive substrate capable ofsupporting a uniform bias potential thereon and at least one coatingcomprising a resilient elastomeric polyurethane formed by reacting:(a) apolyisocyanate prepolymer comprising the reaction product of:(i) asaturated aliphatic polyisocyanate, a saturated cycloaliphaticpolyisocyanate or an aromatic polyisocyanate; and (ii) a polyol free ofaliphatic unsaturation; and (b) a hardening mixture comprising:(i) apolyol of (a) (ii) or a diamine free of aliphatic unsaturation thereof;and, (ii) as a conductivity control agent for controlling theresistivity of the elastomeric polyurethane, from 0.001 to 5.0 weightpercent, based on the total weight of (b), of a complex of ethyleneglycol or an oligoethylene glycol selected from the group consisting ofdi-, tri- and tetraethylene glycol with an ionizable ferric halide saltselected from the group consisting of ferric fluoride, ferric chlorideand ferric bromide,the coating being in electrical contact with theconductive substrate and having an electrical resistivity such that thecoating is capable of transmitting a bias potential from the substrateto the outer periphery of the coating.
 2. The member of claim 1 whereinthe elastomeric polyurethane coating has a resistivity of from about1.0×10⁷ to about 5.0×10¹⁰ ohm cm.
 3. The member of claim 1 wherein theelastomeric polyurethane coating has a resistivity of from about 2.0×10⁸to about 2.0×10¹⁰ ohm cm.
 4. The member of claim 1 wherein theelastomeric polyurethane has a hardness of between about 10 Shore A andabout 80 Shore D.
 5. The member of claim 1 wherein the conductivesubstrate having a coating of elastomeric polyurethane is formed of aconductive metal in the shape of an endless belt.
 6. The member of claim1 wherein the conductive substrate having a coating of elastomericpolyurethane is formed of a conductive metal in the shape of a roll. 7.The member of claim 1 wherein (a) the polyisocyanate in the prepolymeris methylenebis(4-isocyanatocyclohexane), hexamethylene diisocyanate ortoluene diisocyanate and (b) the polyol is poly(oxyethylene glycol),poly(oxypropylene glycol), poly(tetramethylene ether glycol) or mixturesthereof.
 8. The member of claim 1 wherein (a) the polyisocyanate in theprepolymer is methylenebis(4-isocyanatocyclohexane) and (b) the polyolis poly(tetramethylene ether glycol).
 9. The member of claim 1 whereinthe conductivity control agent is present in an amount of 0.001 to 5.0weight percent based on the total weight of (b).
 10. The member of claim1 wherein the conductivity control agent is a complex of ferric chlorideand diethylene glycol.
 11. The member of claim 1 wherein theconductivity control agent is a complex of ferric chloride andtetraethylene glycol.
 12. The member of claim 1 wherein the conductivitycontrol agent for controlling the resistivity further substantiallyreduces the sensitivity of the resistivity to changes in relativehumidity.
 13. The member of claim 1 wherein the conductive supportsurface comprises a photoconductor.
 14. A method of controlling theresistivity of a member for electrically cooperating with a conductivesupport surface to attract charged toner particles from the surfacetowards the member comprising coating a conductive substrate capable ofsupporting a uniform bias potential thereon with at least one layer of aresilient elastomeric polyurethane, said coating being in electricalcontact with the conductive substrate and formed by reacting:(a) apolyisocyanate prepolymer comprising the reaction product of:(i) asaturated aliphatic polyisocyanate, a saturated cycloaliphaticpolyisocyanate or an aromatic polyisocyanate; and (ii) a polyol free ofaliphatic unsaturation; and (b) a hardening mixture comprising: (i) apolyol of (a) (ii) or a diamine free of aliphatic unsaturation, or amixture thereof; and, (ii) as a conductivity control agent forcontrolling the resistivity of the elastomeric polyurethane, from 0.001to 5.0 weight percent, based on the total weight of (b), of a complex ofethylene glycol or an oligoethylene glycol selected from the groupconsisting of di-, tri- and tetraethylene glycol with an ionizableferric halide salt selected from the group consisting of ferricfluoride, ferric chloride and ferric bromide,whereby the elastomericpolyurethane having an altered resistivity is capable of transmitting abias potential from the substrate to the outer periphery thereof. 15.The method of claim 14 wherein the resistivity of the elastomericpolyurethane having the conductivity control agent included therein isfrom about 1.0×10⁷ to about 5.0×10¹⁰ ohm cm.
 16. The method of claim 14wherein the resistivity of the elastomeric polyurethane having theconductivity control agent included therein is from about 2.0×10⁸ toabout 2.0×10¹⁰ ohm cm.
 17. The method of claim 14 wherein theresistivity is increased.
 18. The method of claim 14 wherein theresistivity is decreased.
 19. The method of claim 14 wherein theconductivity control agent is present in an amount of 0.001 to 5.0weight percent based on the total weight of (b).
 20. The method of claim14 wherein the conductivity control agent for altering the resistivityfurther substantially reduces the sensitivity of the resistivity of themember to changes in relative humidity.
 21. The method of claim 14wherein (a) the polyisocyanate in the prepolymer ismethylenebis(4-isocyanatocyclohexane), hexamethylene diisocyanate ortoluene diisocyanate and (b) the polyol is poly(oxyethylene glycol),poly(oxypropylene glycol), poly(tetramethylene ether glycol) or mixturesthereof.
 22. The method of claim 14 wherein (a) the polyisocyanate inthe prepolymer is methylenebis(4-isocyanatocyclohexane) and (b) thepolyol is poly(tetramethylene ether glycol).
 23. The method of claim 14wherein the conductivity control agent is a complex of ferric chlorideand diethylene glycol.
 24. The method of claim 14 wherein theconductivity control agent is a complex of ferric chloride andtetraethylene glycol.
 25. The method of claim 14 wherein the conductivesupport surface comprises a photoconductor.
 26. A method of preventingchanges in the resistivity of members for electrically cooperating witha conductive support surface to attract charged toner particles from thesurface towards the members caused by changes in relative humiditycomprising applying at least one coating of a resilient elastomericpolyurethane formed by reacting:(a) a polyisocyanate prepolymercomprising the reaction product of:(i) a saturated aliphaticpolyisocyanate, a saturated cycloaliphatic, polyisocyanate or anaromatic polyisocyanate; and (ii) a polyol free of aliphaticunsaturation; and (b) a hardening mixture comprising: (i) a polyol of(a) (ii) or a diamine free of aliphatic unsaturation, or a mixturethereof; and, (ii) as a conductivity control agent for controlling theresistivity of the elastomeric polyurethane, from 0.001 to 5.0 weightpercent, based on the total weight of (b), of a complex of ethyleneglycol or an oligoethylene glycol selected from the group consisting ofdi-, tri- and tetraethylene glycol with an ionizable ferric halide saltselected from the group consisting of ferric fluoride, ferric chlorideand ferric bromide,to a cylindrical core of electrically conductivematerial for electrically cooperating with the conductive supportsurface when brought into contact therewith whereby the elastomer iscapable of transmitting a bias potential from the core of electricallyconductive material to the outer periphery thereof and significantreductions in the sensitivity of the resistivity to changes in relativehumidity occur.
 27. The method of claim 26 wherein the conductivitycontrol agent is present in an amount of 0.001 to 5.0 weight percentbased on the total weight of (b).
 28. The method of claim 26 wherein (a)the polyisocyanate in the prepolymer ismethylenebis(4-isocyanatocyclohexane), hexamethylene diisocyanate ortoluene diisocyanate, and (b) the polyol is poly(oxyethylene glycol),poly(oxypropylene glycol), poly(tetramethylene ether glycol) or mixturesthereof.
 29. The method of claim 26 wherein (a) the polyisocyanate inthe prepolymer is methylenebis(4-isocyanatocyclohexane) and (b) thepolyol is poly(tetramethylene ether glycol).
 30. The method of claim 26wherein the conductivity control agent is a complex of ferric chlorideand diethylene glycol.
 31. The method of claim 26 wherein theconductivity control agent is a complex of ferric chloride andtetraethylene glycol.
 32. The method of claim 26 wherein the conductivesupport surface comprises a photoconductor.